Atrioventricular reentrant tachycardia (AVRT) is a common type of SVT and is particularly common in children.
What Is AVRT?
AVRT is a type of reentrant tachycardia. As is the case with all reentrant SVTs, people with AVRT are born with an abnormal electrical connection in the heart. In AVRT, the extra connection, which is often called an accessory pathway, creates an electrical connection between one of the atria (the upper chambers of the heart) and one of the ventricles (the lower chambers of the heart).
Normally, the only electrical connection between the atria and the ventricles is the normal cardiac conducting system, which consists of the AV node and the His bundle.
In people with AVRT, the accessory pathway provides a second electrical connection between the atria and the ventricles. This second connection sets up a potential circuit for establishing a reentrant tachycardia.
How Does AVRT Work?
In a person with an accessory pathway, an episode of AVRT can be triggered by a premature heartbeat—either a premature atrial contraction (PAC) or a premature ventricular contraction (PVC).
This premature beat, if it occurs at just the right time, can trigger a continuous (or reentrant) electrical impulse. This impulse travels down the normal conducting system to the ventricles, then travels back up the accessory pathway to the atria (that is, it “reenters” the atria). It turns around and travels back down the normal conducting system, and repeats.
Thus, a single premature beat establishes a sudden tachycardia.
The symptoms of AVRT are typical for SVT. They most often include one or more of the following:
PalpitationsLightheadednessDizziness
Episodes usually last from a few minutes to several hours.
How Can AVRT Be Stopped?
AVRT can be stopped by a PAC, a PVC, or simply by slowing electrical conduction through the AV node. Any of these events can interrupt the reentrant impulse.
The fact that slowing AV node conduction can stop AVRT gives a person with this arrhythmia an opportunity to make it go away.
People with AVRT can often stop an acute episode by taking action to increase the tone of their vagus nerve, which richly supplies the AV node.
This can be accomplished, for instance, by performing a breathing technique known as the Valsalva maneuver, or by immersing your face in ice water for a few seconds.
AVRT and Wolff-Parkinson-White Syndrome
In some people with AVRT, the accessory pathway is capable of conducting electrical impulses in either direction (that is, from the atrium to the ventricle, as already described, or from the ventricle to the atrium). In other people, the accessory pathway can only conduct electrical impulses in one direction or the other.
This difference turns out to be important. In most people with AVRT, the impulses can only go across the accessory pathway from the ventricle to the atrium.
When the impulses are able to cross in the other direction (from the atrium to the ventricle) Wolff-Parkinson-White (WPW) syndrome is present. WPW is associated with more clinical problems than typical AVRT.
Because the pathway in WPW can allow irregular atrial activity to affect the ventricles which may lead to death, it often needs to be treated more aggressively.
Treating AVRT
If WPW is not present and symptoms of AVRT are rare and easily stopped (say, by performing a Valsavla maneuver), then treatment may not be necessary beyond learning what to do when an episode occurs.
However, if you have WPW, frequent episodes of SVT, particularly severe symptoms during episodes, or have trouble stopping episodes when they occur, then more definitive treatment should be used.
Antiarrhythmic drug therapy is often partially effective at preventing episodes of AVRT.
However, in most people with AVRT, ablation therapy is able to get rid of the accessory pathway altogether and completely prevent any further episodes. With modern techniques, ablating accessory pathways can be accomplished successfully and safely in the vast majority of cases.
A Word From Verywell
Atrioventricular reentrant tachycardia (AVRT) is a common variety of SVT. While it frequently produces significant symptoms and can be quite disruptive to life, AVRT today is often curable with ablation.
